This invention relates to a device and a method for measuring the dynamic pressure of a combustion chamber of, for example, a gas turbine machine.
As part of the monitoring controls and diagnostic tools for an operating combustion system in a rotary machine such as a gas turbine, it is necessary to measure and acquire various data including combustion chamber dynamic pressure. This data is used to confirm proper operational health of the combustion system, and is also used to tune the gas turbine engine so that it is operating with an appropriate balance between combustion dynamics and emissions. Measuring dynamic pressure directly in a combustion chamber requires a sensor that functions in operating environments having temperatures in the range of 2000-3000° F. Currently, existing dynamic pressure probes are designed to withstand no more than about 1000° F. As a result, existing combustion dynamic pressure measurement methods do not utilize sensors located directly on the combustion chamber. Rather, current systems use metal tubing called wave guides to transmit the pressure signal from the combustion chamber to a remotely located dynamic pressure sensor. The long length of the metal tubing from the combustion chamber to the remotely located sensor results in significant attenuation of the pressure signal, so that it is not possible to measure the true dynamic pressure of the combustion system. In these systems, several factors affect the degree of signal attenuation, including, the internal diameter of the tubing; the length of the tubing; the temperature profile within the tubing; the static pressure within the tubing; and the frequency content of dynamic pressure signature. In some systems, a damping coil wound around an axis is used to prevent the formation of standing waves in the measurement system. This type of system results, however, in the formation of condensate in the wound damping coil. Condensation build up in the coils results in standing waves being formed in the tubing which attenuates the true source signal and prevents it from being measured accurately.
Thus, in order for an acoustic damping system to work continuously, the formation of condensation in a coil system must be prevented. To address this issue, conventional systems must be periodically purged to remove the condensate from the damping coils.